Help With Making a Splash Effect

[Tygra]

So, I have made the image much, much smaller, and the xcf file is now under 2 MB.

What I mean is I have put a layer of a tiger splashing through water underneath the tiger I want to keep. 

I then apply a layer mask to the tiger image that I am keeping.

I then brush out the tiger that is underneath, creating the splash around the tiger than I am keeping.

However, then I still have the background from the layer that is underneath.

Hence, I am wondering if there is any simple way to remove the remaining background?